JPH041740B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL FIELD The present invention relates to a process for producing thiuram polysulfide from secondary amines, carbon disulfide and sulfur in the presence of an oxidizing agent. PRIOR ART Thiuram polysulfides are used in particular as sulfur donors and accelerators in the vulcanization of rubber. These substances are commercially available, for example, under the names thiuram tetrasulfide (tetramethylthiuram tetrasulfide or dipentamethylenethiuram tetrasulfide) or thiuram hexasulfide (dipentamethylenethiuram hexasulfide). There is. The chemical structure of these products is not precisely known as there have been no analytical methods to distinguish between mixtures of different polysulfides and mixtures of polysulfide and sulfur. Furthermore, thiuram polysulfides are easily decomposed substances that tend to eliminate sulfur, especially in the dissolved state. This problem can be seen, for example, in the West German patent publication number.
2725166 details an example of a material described as tetramethylthiuram tetrasulfide. By using modern analytical methods such as high pressure liquid chromatography (HPLC) and gel permeation chromatography (GPC), the above commercial products are no longer single compounds, but vary with their respective manufacturing methods. It was shown in quality that it is a mixture of many polysulfides and free sulfur with a composition of a certain amount. In general, the preparation of thiuram polysulfides starts from the corresponding dithiocarbamates, which are usually prepared from secondary amines, carbon disulfide and alkali metal hydroxides or alkaline earth metal hydroxides. Thus, US Pat. No. 1,681,717 and US Pat. No. 1,780,545 have the following reaction formula: describes a method for producing thiurapolysulfide by reacting a dithiocarbamate with sulfur chloride. However, very low yields are achieved here. An improved method for producing thiuram tetrasulfide, in particular dipentamethylenethiuram tetrasulfide, using sulfur monochloride based on the above reaction scheme is described in US Pat. No. 2,414,014. Yields up to 95% were achieved with this method. However, all these methods have the disadvantage that they have to work with sulfur chloride, which is corrosive and has an unpleasant odor, and additionally large amounts of unusable salts are produced as problematic by-products. have. A process which eliminates the additional formation of sodium chloride is described in DE 27 25 166 A1. According to this method, dimethylammonium dimethylthiocarbamate is reacted with hydrogen peroxide in the presence of carbon disulfide and sulfur to form tetramethylthiuram tetrasulfide. In a variant of this process according to DE 27 25 166, the dithiocarbamate salt to be reacted is formed from dimethylamine and carbon disulphide in water in a pre-reaction step and subsequently the dimethylammonium salt obtained in this case is The aqueous solution of dimethylthiocarbamate is further reacted with sulfur and hydrogen peroxide in the same reaction vessel to give tetramethylthiuram tetrasulfide. Thus, according to example 1 of West German Patent Publication No. 2725166,
Fill the reaction vessel with water, dimethylamine and 2 drops of nonionic surfactant, stir the solution at 25°C, and add carbon disulfide over 14 minutes, increasing the temperature to 35°C. . Add a small amount of sulfur,
Then water is added. Next, carbon disulfide is added simultaneously with hydrogen peroxide to the resulting suspension over a period of 60 minutes, with hydrogen peroxide being added 2 minutes after the start of the addition of carbon disulfide. Finally, the final product is obtained by filtration with a yield of 90%. Although the process is certainly an improvement over the process described at the outset, its use is limited to the production of tetramethylthiuram tetrasulfide. Other disadvantages are the relatively high and less selective oxidizing agent (hydrogen peroxide), the need for nonionic surfactants and non-quantitative yields. For the production of thiuram sulfide, a third
A less expensive process by reaction of a secondary amine and carbon disulfide in the presence of a primary amine and an oxidizing agent is described in West German patent application no. 3105587.7. This process using metal-containing catalysts and oxygen as oxidizing agent leads to thiuram disulfide in high yields. Problems to be Solved by the Invention Furthermore, there is a need for an easy process for producing thiuram polysulfide from cheap starting materials in high yields. Means for Solving the Problems Such a problem consists in replacing a thiuram polysulfide substituted with an aliphatic, araliphatic, cycloaliphatic and/or aromatic hydrocarbon with a correspondingly substituted second thiuram polysulfide.
This reaction is carried out in the presence of a tertiary amine at a temperature of 0 to 150°C to produce the product by reacting a primary amine with carbon disulfide and sulfur in a solvent in the presence of an oxidizing agent.
The present invention is solved by a process for the preparation of substituted thiuram polysulfides, which is carried out at a temperature of The process according to the invention is suitable for the production of a large number of different sulfur-containing, highly differently substituted thiuram polysulfides. The use of only one secondary amine as a reaction component gives thiuram polysulfides with the same substitution on both nitrogen atoms. When two different secondary amines are used as reaction components, thiuram polysulfides with two differently substituted nitrogen atoms are obtained depending on the respective process conditions (amine basicity difference, molar ratio, etc.); At this time, a rather large amount of thiuram polysulfide, in which both sides are symmetrically substituted, is produced as a by-product. The length of the sulfur bridge in the thiuram polysulfide is determined by the amount of sulfur used. For example, if one gram atom of sulfur is used per mole of secondary amine, a product with sulfur bridges of on average 4 sulfur atoms (tetrasulfide) is obtained. Using 2 gram atoms of sulfur per mole of amine yields, on average, hexasulfide. All secondary amines are suitable for this process. This type of secondary amine has the formula [Here, R ₁ and R ₂ may be the same or different and each represents a C ₁ -C ₁₈ -alkyl group, such as methyl, ethyl, propyl, n-butyl, t-butyl, hexyl, dodecyl and octadecyl, cyclo alkyl groups, such as cyclopentyl and cyclohexyl groups and cyclopentyl and cyclohexyl groups substituted by alkyl groups, and _C1 - _C18 -alkyl groups substituted by aryl groups, such as phenyl and naphthyl groups, and aromatic groups,
For example, phenyl and naphthyl groups, phenyl and naphthyl groups substituted by alkyl groups, and phenyl and naphthyl groups substituted by alkyl groups]. The secondary amine substituents may be linked to each other via covalent bridge members. Examples of amines of this type are piperidine, pyrrolidine, morpholine and its derivatives and other nitrogen-heterocycles. Suitable tertiary amines are aliphatic, cycloaliphatic and/or aromatic substituted amines and heterocycles with trisubstituted nitrogens. Tertiary amines with pKa>8, such as trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine,
n-octyl-dimethylamine, ethyldimethylamine, propyldimethylamine, butyldimethylamine, tetramethylethylenediamine, N-
Methylpyrrolidine, N-dimethylamino-pyridine and 1,4-diazabicyclo-(2,2,2)-
Advantageously, octane is used. The amount of tertiary amine can vary within wide limits. The range extends from catalytic amounts to stoichiometric and even amounts corresponding to or exceeding the amount of solvent. The tertiary amine can also act as a solvent. The oxidizing agent in the process according to the invention is oxygen or an oxygen-containing gas, especially air. Sulfur can be added solid, liquid or dissolved in, for example, carbon disulfide. It has now been found that the method of the invention is a completely new type of reaction. Thus, it was surprising that a significantly higher oxidation rate was achieved in this reaction than in the corresponding reaction leading to simple thiuram disulfide without the addition of sulfur; This means that it has a strong promoting effect on In the process of the invention, the solvent is less critical and can be used in various groups of substances, for example aromatic hydrocarbons such as benzol, toluol, xylol, nitrobenzole, aliphatic esters, alkyl ethers, lower alcohols such as methanol, ethanol, isopropanol, n -propanol, n
- butanol, tert-butanol and amyl alcohol, also chlorohydrocarbons such as dichloromethane, chloroform, dichloroethane, trichloroethane, also aprotic solvents such as dimethylformamide, acetonitrile, dimethylacetamide, dimethylsulfoxide and hexamethylphosphoric triamide, and water or the solvents mentioned. Mention may be made of mixtures of. Due to the secondary amines used, high yields and selectivities can be achieved in some cases in pure water.
However, reaction rates in water are generally lower than in the non-aqueous solutions mentioned above. Preference is given to using aromatic hydrocarbons, lower alcohols having up to 6 carbon atoms, mixtures of these solvents or mixtures of these lower alcohols with water as solvents. Suitable metal-containing catalysts are all metals of the subgroups whose valences can be easily converted and their derivatives. As metal-containing catalysts, preference is given to using cerium, manganese, copper, iron, cobalt, molybdenum or vanadium in elemental form or in the form of salts, oxides, complexes or organic compounds thereof. Among the preferred metals or their derivatives, copper, manganese and cerium have a higher catalytic activity compared to iron, cobalt, molybdenum and vanadium, but the latter group of metals and their derivatives are also excellent for oxidation. It is a catalyst. Elemental copper is advantageously used as copper powder.
All monovalent or divalent inorganic copper compounds,
Mention may be made of organic, simple or complex copper salts. For example, suitable monovalent copper salts include copper chloride (), copper oxide (), copper iodide (), addition products of these copper halides () and carbon monoxide, copper complexes ()
Salts, such as alkali metal chlorocuprates, ammonia complex compounds of copper() cyanide, such as cyanocuprates, such as potassium-tricyanoprates.
(), copper rhodanate (), a double salt with copper acetate () and copper sulfide (), and a double sulfide from copper sulfide () and an alkali polysulfide. For example, suitable copper () salts include copper chloride (), copper bromide (), copper sulfide (), copper sulfate (), copper nitrate (), copper nitrite (), copper rhodanate (), copper cyanide () ),
Copper() salts of carboxylic acids, such as copper() acetate,
It is an ammonia complex compound of copper dithiocarbamate and copper-()-salt. Copper oxide () is also very suitable as a catalyst. For example, suitable manganese-containing catalysts are manganese powder, manganese dioxide, potassium permanganate, manganese acetate and manganese dithiocarbamate and other manganese derivatives corresponding to the copper compounds mentioned above. Examples of suitable cerium catalysts include metallic cerium, cerium dioxide, cerium chloride (),
Cerium chloride () and cerium chloro complex salt,
Mention may be made of cerium nitrate and cerium nitrate salts, cerium sulfate, cerium carbonate, cerium oxalate and cerium. Examples of iron catalysts are the known iron oxides, iron() salts and iron() salts and complex salts. Examples of suitable vanadium catalysts are vanadium oxide,
Vanadium chloride and vanadium sulfate as well as known double salts and complex salts. Suitable cobalt catalysts are the known cobalt oxides, cobalt() salts and complex salts. Finally, examples of suitable molybdenum catalysts include oxides, chlorides, sulfides and fluorides, as well as molybdates and the known complex acid salts. Of course, mixtures of a number of the abovementioned catalysts can also be used. The amount of metal-containing catalyst required is surprisingly small.
The amount is advantageously in the range from 0.01 to 5 mmol per mole of secondary amine. It is also possible to use smaller amounts of catalyst, but in this case longer reaction times must be accepted. The use of larger amounts of catalyst is not recommended as there is a risk that the catalyst will precipitate and impure the reaction product. The method according to the invention comprises a temperature in the range 0 to 150°C;
It is preferably carried out at 20-90°C. Temperatures above 90° C. increase the space/time yield, but are not very advantageous from a safety point of view. It is advantageous to carry out the process according to the invention at an oxygen pressure or oxygen partial pressure of at least 0.1 bar. As expected, the reaction rate increases with increasing pressure. For reasons of technical safety, a pressure range of 1 to 10 bar is advantageous. For carrying out the process, the reaction components, catalyst and solvent are combined in each case in any order. Secondary amine and carbon disulfide are generally used in an approximately stoichiometric ratio (1:1); carbon disulfide is preferably used in a slight excess (0.01 to 0.2 molar excess). The amount of sulfur to be used can vary within a wide range, depending in each case on the desired end product. Amounts of 1 to 3 gram atoms of sulfur/mol of secondary amine are advantageous. Using 1 gram atom of sulfur per mole of secondary amine gives primarily thiuram tetrasulfide, using 2 gram atoms of sulfur gives thiuram hexasulfide, and at higher amounts of sulfur Correspondingly high thiuram polysulfides are produced. Particular preference is given to using 1 to 2 gram atoms of sulfur per mole of secondary amine. According to an embodiment of the invention, the secondary amine, carbon disulfide, sulfur, tertiary amine and metal-containing catalyst are dissolved or suspended in a solvent and in the presence of oxygen or an oxygen-containing gas. Conversion to the corresponding thiuram polysulfide. Isolating the dithiocarbamate formed as an intermediate from the secondary amine, carbon disulfide and the tertiary amine and subsequently reacting the dithiocarbamate with sulfur in the presence of oxygen or an oxygen-containing gas and a metal-containing catalyst. is also possible. Furthermore, it is also possible to introduce the reaction components secondary amine, carbon disulfide and sulfur into the reaction solution during the reaction. The reaction time depends on the process conditions as well as the secondary amine used, and generally reaction times range from several minutes to several hours. Under favorable conditions regarding temperature and oxygen pressure, the reaction time is from a few minutes to 1 hour. In carrying out the process according to the invention, oxygen or an oxygen-containing gas is pressurized into the reaction mixture under the stated pressure and temperature conditions or introduced into or through the reaction mixture. The end of the reaction (complete conversion) can be detected in a simple way, for example by the end of oxygen uptake. In many cases, for example in tetramethylthiuram polysulfide or dipentamethylenethiuram polysulfide, the final product immediately precipitates out of the reaction mixture as a solid and can be filtered off. In other cases, the desired product is obtained by cooling or concentrating the reaction mixture. Liquid products are obtained in pure form by distillation or extraction processes. In the industrial implementation of the process according to the invention, it is advantageous to circulate the mother liquor, which mainly consists of solvent, tertiary amine and metal-containing catalyst, with fresh tertiary amine or metal-containing catalyst being recycled. It is not necessary to always add For example, more than 10 reaction cycles can be carried out with the same mother liquor in consistently high yields without any observed decrease in the catalytic activity of the mother liquor. In the method according to the invention, in most cases 99%
Larger, virtually quantitative yields and selectivities were achieved. The products occur in high purity and can generally be subjected to their determination without purification. With the corresponding addition of sulfur, the products obtained correspond in their chemical composition to the commercially available products (for example tetramethylthiuram tetrasulfide, dipentamethylthiuram tetrasulfide or dipentamethylenethiuram hexasulfide). do. First, compared to the known two-step method for synthesizing dithiocarbamates, the one-step method does not use any auxiliary agents and is therefore superior in terms of its economy and lack of environmental pollution. In contrast to the process known from DE 27 25 166, which is limited only to the production of tetramethylthiuram tetrasulfide, although in one step, the process of the present invention is a simple reaction process and significantly cheaper. It has the advantage that oxidizing agents can be used and virtually quantitative yields and high selectivities can be achieved. EXAMPLES Next, the present invention will be explained in detail with reference to examples. Example 1 Double jacket for circulation of heating liquid, thermometer,
34.06 g (0.4 mol) of piperidine, 20.2 g of triethylamine in 280 ml of methanol in a 1-glass autoclave equipped with a pressure measuring device and a stirring device.
(0.2 mol) and manganese acetate () tetrahydrate
Add 25.64 g (4.8 gram atoms) of sulfur and 31.2 g (0.41 mole) of carbon disulfide to a solution of 4.9 g (0.02·10 ⁻³ mole). The reaction mixture was heated to 50°C, stirred vigorously and 1.8 bar of oxygen was added. Oxygen consumption is immediately noted and an almost white precipitate forms. After 55 minutes,
The reaction ends (oxygen uptake no longer takes place). Piperidine converts completely. The precipitate formed is filtered off, washed with methanol and dried.
87.8 g of product with a melting range of 124-127°C are obtained. The product corresponds in composition to dipentamethylenethiuram hexasulfide. Analysis: Dipentamethylene thiuram hexasulfide C ₁₂ H ₂₀ N ₂ S ₈ Calculated values: C32.11% H4.49% N6.24% S57.15% Actual values: C32.2% H4.6% N5. 9% S57.4% High pressure liquid chromatography analysis demonstrated that the content of free sulfur and dipentamethylenethiuram disulfide in the product were each lower than 1%. The mother liquor also contains 1.2 g of product, which can be isolated by concentration or intensive cooling; the triethylamine used is contained unchanged in the mother liquor. This gave a total yield of 89.0 g, corresponding to 99.1% of the theoretical value. The product produced by this method corresponds to a product called dipentamethylenethiuram tetrasulfide, which is commercially available as a sulfur donor. Example 2 (Comparative): Proceed as in Example 1, but without adding sulfur. In this case, the oxidation leading to dipentamethylenethiuram disulfide takes place very slowly.
After a reaction time of 55 minutes, the reaction mixture contained only a small amount of dipentamethylenethiuram disulfide with a melting point of 132°C.
Contains 11.2g (corresponding to 17.5% of the theoretical value). This example shows that sulfur strongly promotes the reaction. Example 3: 78.7 g of triethylammonium pentamethylene dithiocarbamate (0.3
mol) of methanol in the reactor described in Example 1.
6.1 mg of manganese acetate () tetrahydrate in 300 ml
(0.025・10 ^-3 mol) of sulfur 9.6 g (0.3 mol)
and oxygen as described in Example 1. The reaction temperature is 50°C, the oxygen pressure is 1.7 bar, and the reaction time is 70 minutes. A product with a melting range of 123 DEG to 128 DEG C. is obtained, which corresponds in composition to dipentamethylenethiuram tetrasulfide. Analysis: dipentamethylenethiuram tetrasulfide C ₁₂ H ₂₀ N ₂ S ₆ Calculated values: C37.46% H52.4% N 7.28% S50.01% Actual values: C37.4% H 5.1% N50.2% The amount of free sulfur is lower than 1% (HPLC-analysis)
Yield: 56.9g (98.7% of theoretical value). Example 4 To prepare N,N'-dimethyl-N,N'-diphenyl-thiuram polysulfide, 32.15 g (0.3 mol) of N-methylaniline, 23.6 g (0.31 mol) of carbon disulfide in 300 ml of methanol, 31.37 g (0.31 mol) of triethylamine and 9.6 g (0.3 gram atom) of sulfur are reacted with oxygen in the manner described in Example 1.
As a catalyst, 0.1·10 ⁻³ mol of manganese acetate () is used, the reaction temperature is 50° C., and the oxygen pressure is 1.8 bar. After 150 minutes, the experiment was stopped and the resulting fine, slightly yellow precipitate was filtered off, washed and
dry. The composition of the resulting product in the melting range of 160-170 DEG C. corresponds to N,N'-dimethyl-N,N'-diphenylthiuram tetrasulfide. Analysis: N,N'-dimethyl-N,N'-diphenylthiuram tetrasulfide C ₁₆ H ₁₆ N ₂ S ₆ Calculated value: C44.8% H3.8% N6.5% S44.9% Actual value :C44.4% H3.6% N6.2% S45.5% Yield is 58.4g (90.8% of theoretical value). Example 5: (Comparative) Treat as in Example 4, but without adding triethylamine. Under these conditions virtually no oxygen uptake occurs. It can be seen that after a reaction time of 150 minutes, the substances used remain unchanged. Example 6 In the reactor described in Example 1, morpholine
34.8g (0.4mol), carbon disulfide 31.2g (0.41mol), triethylamine 20.2g (0.2mol) and sulfur 25.64g
(0.8g atom) to manganese acetate ()0.025.
Reacts with oxygen in the presence of 10 ^-3 mol. The reaction temperature is
The temperature is 50°C and the oxygen pressure is 1.7 bar. After 270 minutes, stop the experiment. The colored fine precipitate is filtered off, washed and dried. Melting range 119~122
The resulting product at ℃ is di-N,
Corresponds to N'-oxydiethylene-thiuram hexasulfide. Analysis: Di-N,N'-oxydiethylenethiuram hexasulfide C ₁₀ H ₁₆ N ₂ O ₂ S ₈ Calculated values: C26.53% H3.56% N6.19% S56.65% Actual values: C26. 3% H3.5% N6.0% S56.9% Yield: 84.0 g (92.8% of theory). Example 7 (Comparative Example) Work as in Example 6, but without adding triethylamine. Oxygen uptake takes place very slowly under these conditions; after 270 minutes a reaction mixture is obtained which mainly contains the individual starting components in unchanged form or as dithiocarbamates. Example 8: 34.8 g (0.4 mol) of morpholine, 31.2 g (0.41 mol) of carbon disulfide, 24.2 g of trimethylamine in 300 ml of isopropanol in the reactor described in Example 1.
(0.41 mol) and 12.8 g (0.4 mol) of sulfur are reacted together with oxygen, using 0.2.10 ^-3 mol of manganese acetate () as catalyst. Reaction temperature is 60℃
and the oxygen pressure is 1.8 bar. The reaction ends after 90 minutes. By filtering and washing the resulting precipitate, 73.1 g of di-N,N'-oxydiethylenethiuram tetrasulfide (theoretical value) with a melting range of 120 to 130°C was obtained.
94.1%) is obtained. Examples 9 to 12; carried out as in Example 1, but using other catalysts and different reaction temperatures. The corresponding reaction times and product yields are listed in Table 1.

Table Examples 13 to 16 As in Example 1, but using other solvents. The results are listed in Table 2.

[Table] Example 17 In this example, air is used as the oxygen-containing gas. Using the same method as in Example 1, 34.5 g (0.4 mol) of piperidine, 31.2 g (0.41 mol) of carbon disulfide,
mol), triethylamine 9.9 g (0.1 mol) and sulfur 12.8 g (0.4 g atom) manganese acetate ()
The reaction is carried out in the presence of 0.025.10 ^-3 mol and air (total pressure 5 bar). The reaction temperature is 50°C and the reaction time is 120 minutes. In this case, a yield of 75.2 g of dipentamethylenethiuram polysulfide is obtained (97.9% of theory). Examples 18-21 Other secondary amines are used in the following examples. The experiments are carried out in each case according to the method described in Example 1. Methanol as the solvent
300 ml is used and the oxygen pressure is 1.7 bar. Other reaction conditions as well as yields and melting points of the corresponding thiuram polysulfides are given in Table 3 below.

【table】

Claims (1)

[Scope of Claims] 1 Thiuram polysulfide substituted with aliphatic, araliphatic, cycloaliphatic and/or aromatic hydrocarbons, a correspondingly substituted secondary amine, carbon disulfide and prepared by reacting with sulfur in a solvent in the presence of an oxidizing agent, this reaction is carried out in the presence of a tertiary amine at a temperature of 0 to 150 °C,
A method for producing a substituted thiuram polysulfide, characterized in that the oxidizing agent is oxygen or an oxygen-containing gas and a metal-containing catalyst. 2 Carbon disulfide 1 to 1 mole of secondary amine
A method according to claim 1, in which 1.2 mol is used. 3. A process according to claim 1 or claim 2, wherein from 1 to 3 gram atoms of sulfur are used per mole of secondary amine. 4. A process according to claim 1, wherein the metal-containing catalyst is used in an amount of 0.01 to 5 mmol per mole of secondary amine. 5. Claims 1 to 4 in which cerium, manganese, copper, iron, cobalt, molybdenum or vanadium is used as a catalyst in elemental form as a salt, oxide, complex or organic compound or a mixture thereof. The method described in any one of the above. 6. Process according to any one of claims 1 to 5, characterized in that a tertiary amine with a pKa value >8 is used. 7. Claims 1 to 6 that use optionally substituted aromatic hydrocarbons, lower alcohols having up to 6 carbon atoms, mixtures of these solvents, or mixtures of lower alcohols and water as solvents. The method according to any one of the above. 8. The method according to any one of claims 1 to 7, wherein the reaction is carried out at a temperature of 20 to 90°C.